The present invention relates, in general, to the field of standing timber diameter measurement and basal area determination devices and methods. More particularly, the present invention relates to an upper stem diameter measurement (xe2x80x9cUSDMxe2x80x9d) and basal area determination device and method of especial utility in determining the merchantable volume of standing trees in timber cruising operations.
Among the steps necessary in planning management activity with respect to forested land is to conduct an inventory of available resources, (sometimes referred to as timber xe2x80x9ccruisingxe2x80x9d), in which the available timber volume, or board feet of lumber, among harvestable trees is determined. In this regard, direct or indirect measurements of a particular tree""s height and diameter may be taken with or without a determination of 80% stem diameter at breast height (xe2x80x9cDBHxe2x80x9d) or other recordation of tree stem height at a predetermined fixed stem width above its base. Other cruising operations may include a determination as to which trees within a specified area of observation are determined to be xe2x80x9cinxe2x80x9d or xe2x80x9coutxe2x80x9d with respect to subsequent harvesting based upon a specified basal area function.
Currently, a number of tools and types of equipment are available for undertaking these types of measurements including: tape measures, calipers and scale sticks for measuring diameters, all of which require the timber cruiser to physically access each individual tree. Determinations of tree heights may be made remotely by existing hypsometers while distance measurements can be effectuated by any number of laser-based distance measuring and ranging instruments.
Certain other instruments are currently available which attempt to combine a number of cruising functions into a single portable device. Representative of these is the Spiegel Relaskop and Telerelaskop (Salzburg, Austria) which are relatively awkward to use, failure prone in the field and ultimately imprecise optical/mechanical instruments for measuring range, tree height, diameter and certain tree stand parameters. A more robust and accurate instrument for timber cruising applications is the Criterion 400 series of survey lasers manufactured and distributed by Laser Technology, Inc., Englewood, Colo., assignee of the present invention.
However, a need still exists for a compact, portable upper stem diameter measurement (xe2x80x9cUSDMxe2x80x9d) device which is rugged and self-contained for use in determining tree stem diameter at many points along the stem, height, 80% DBH measurements and basal area function computations which may be utilized by itself or in conjunction with a commercially available laser-based range finder such as the Impulse series also available from Laser Technology, Inc.
Disclosed herein is an upper stem diameter measurement (xe2x80x9cUSDMxe2x80x9d) device which is operative to more quickly and accurately provide a user with much improved functionality over that of a conventional and relatively expensive optical/mechanical Spiegel Relaskop or Telerelaskop for use in timber cruising activities. In an exemplary embodiment disclosed herein, the device may be used alone or in operative association with a laser-based distance measuring and ranging instrument which may be coupled to it by means of a built in serial port.
In one implementation of the present invention, a viewing window is provided in which are projected variable, visual brackets for alignment by the user, or automatic adjustment under processor section control, with the left and right sides of a target tree stem or trunk. The device further includes a built-in inclinometer such that computations of height and stem diameter can be automatically adjusted depending on the user""s line of sight with respect to a horizontal plane. A preferred embodiment disclosed herein includes a user actuatable keypad for inputting data, such as a desired operational mode, a specified basal area factor and the like, a user viewable display as well as control buttons for adjusting the visual brackets and indicating an acceptance of various of the device parameters and operational characteristics.
Operationally, in addition to determination of tree height (of substantially vertical or leaning trees) from an observation point either above or below the base of the tree, the USDM device of the present invention is operative to determine tree diameter by visually bracketing the perceived diameter of the tree at a given point on the tree. With knowledge of the horizontal distance to the tree and the vertical angle of the line of sight to the selected point, the height and diameter of the tree at that point can be automatically determined. When used in an 80% DBH (or fixed width at the upper stem) mode, the device automatically sets the visual brackets to the selected value. The user then aims the device up the tree stem until the brackets are aligned with the left and right sides of the stem as viewed between the brackets and the height of the tree at which 80% DBH (or a fixed width) occurs is calculated and displayed. For use in a function in which basal area is to be determined, the basal area factor is entered into the keypad whereupon the device automatically sets the visual brackets a predetermined distance apart corresponding to a fixed angular subtense in the horizontal plane. The device is then aimed at a series of trees which, if their perceived diameter is greater than or equal to what is shown in the visually adjacent brackets, are then considered to be xe2x80x9cinxe2x80x9d, otherwise they are determined to be xe2x80x9coutxe2x80x9d as being too small.
Particularly disclosed herein is a device for remotely determining a diameter of a substantially conical object which comprises a display for superimposing a user viewable image over a face of the object along a desired line of sight. The display produces visually adjustable brackets for alignment with the perceived left and right sides of the object face. A user input device is provided for manually aligning the adjustable brackets with the left and right sides of the object face. An inclinometer is also provided for producing an electrical indication of a vertical angle of the line of sight while a processor section calculates the diameter of the object based upon a known horizontal distance to the object, the electrical indication of the vertical angle of the line of sight and a separation between the adjustable brackets.
Further disclosed herein is a device for determining a height of a substantially conical object at which a selected diameter occurs. The device comprises a display for superimposing a user viewable image over a face of the object along a desired line of sight, with the display producing visually adjustable brackets for alignment with perceived left and right sides of the object face. A user input device allows for manual entry of a selected diameter while an inclinometer produces an electrical indication of an angle of the line of sight. A processor section automatically adjusts a spacing between the brackets based upon a known horizontal distance to the object, the electrical indication of the angle of the line of sight and the selected diameter.
Also disclosed herein is a device for determining a basal area of a stand of trees which comprises a display for superimposing a user viewable image over a face of selected ones of the stand of trees along a desired line of sight. The display produces visually adjustable brackets for alignment with perceived left and right sides of the face of the selected ones of the stand of trees. A user input device is provided for manually entering a selected basal area factor and an inclinometer produces an electrical indication of a vertical angle of the line of sight. A processor section automatically adjusts a spacing between the brackets based upon the electrical indication of the vertical angle of the line of sight and the selected basal area factor to provide a fixed angular subtense in the horizontal plane.